Assembly of quasicrystalline photonic heterostructures

ABSTRACT

A method and system for assembling a quasicrystalline heterostructure. A plurality of particles is provided with desirable predetermined character. The particles are suspended in a medium, and holographic optical traps are used to position the particles in a way to achieve an arrangement which provides a desired property.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present application claims priority to U.S. patent application Ser.No. 13/163,460, filed Jun. 17, 2011, which is a divisional applicationof Ser. No. 11/483,021, filed Jul. 7, 2006, now U.S. Pat. No. 7,981,774,and U.S. Provisional Application No. 60/697,872, filed on Jul. 8, 2005,all of which are incorporated herein by reference in their entirety.

This work was supported by the National Science Foundation through GrantNumbers DMR0451589, DMR021306 and DMR0243001, and US Department ofEnergy grant DE-FG02-91ER40671.

FIELD OF THE INVENTION

This invention relates generally to the field of quasicrystallineheterostructures. More particularly the invention relates to theassembly of quasicrystalline photonic heterostructures with specifiedorientational symmetry in two dimensions, or along any two dimensions ina three-dimensional structure, or with any specified three-dimensionalquasicrystalline symmetry, and also the use of holographic optical traps(HOTS) to perform that assembly and to the use of those HOTS assembledstructures for a variety of uses.

BACKGROUND OF THE INVENTION

Crystalline materials have long been exploited in many optical andelectronic applications for physical properties arising from theircrystalline symmetry. Although such crystalline materials allow manytechnological applications to be fulfilled, there are limitationsimposed by such crystalline symmetry. For example, ordered arrangementsof dielectric materials with alternating domains of high and low indexof refraction are known to exhibit a property for the transmission oflight known as a photonic bandgap. The optical properties of a photonicbandgap material are characterized by a range of frequencies of lightfor which light cannot propagate, nor is it absorbed. This property isanalogous to the electronic bandgaps that arise in semiconductors forthe transport of electrons, and should result in a similarly broadspectrum of applications. The extent of a material's photonic bandgapdepends both on the dielectric properties of the constituent dielectricmaterials and also on the symmetries of their three-dimensionalarrangement. The limited set of distinct symmetries available forcrystalline arrangements require a very large contrast in dielectricconstant to achieve a full photonic bandgap, and these symmetries resultin optical materials whose optical properties are very sensitive tostructural and chemical defects. By contrast, quasicrystals are knownthat have far higher rotational symmetries than is possible forcrystals. They consequently should exhibit larger and more uniformphotonic bandgaps than any crystalline arrangement of the samematerials, and should have optical properties that are more robustagainst defects and disorder. Two-dimensional and three-dimensionalquasicrystalline arrangements of materials therefore should have a widerange of technological applications based on their optical and otherphysical properties.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide an improved systemand method for fabricating quasicrystalline structures.

It is another object of the invention to provide an improved system andmethod for fabricating quasicrystalline photonic heterostructures usingholographic optical traps.

It is also an object of the invention to provide an improved article ofmanufacture of a three dimensional quasicrystalline photonicheterostructure.

It is a further object of the invention to provide an improved systemand method for constructing materials having photonic band gapsforbidden in crystalline materials.

It is yet another object of the invention to provide an improved systemand method for constructing rotationally symmetric heterostructureshaving optical, mechanical, chemical, biological, electrical andmagnetic properties unachievable by crystalline materials.

It is an additional object of the invention to provide an improvedquasicrystalline heterostructure having programmable optical,mechanical, biological, electrical, magnetic and chemical properties.

It is also another object of the invention to provide an improved systemand method for constructing a quasicrystalline structure with specifiedBrillouin zones for selected technological applications.

It is also a further object of the invention to provide an improvedsystem and method for constructing a quasicrystalline material with asubstantially spherical Brillouin zones.

It is yet an additional object of the invention to provide an improvedsystem and method for constructing a quasicrystalline material havinglong range orientational order without transitional periodicity andconstructed to operate in a predetermined manner responsive to at leastone of an electrical field, a magnetic field and electromagneticradiation.

It is also a further object of the invention to provide an improvedsystem and method for constructing quasicrystalline heterostructureswhich can be switched from one structural state to another state byrepositioning particles to thereby modify physical, biological, andchemical properties of the arrangement.

It is still another object of the invention to provide an improvedsystem and method for constructing quasicrystalline heterostructures byuse of holographic optical traps to dynamically modify chemical andphysical properties in accordance with time sensitive requirements.

It is another object of the invention to provide an improved system andmethod for constructing quasicrystalline heterostructures havingholographic optical traps to form engineered features which enablecreation of narrow band waveguides and frequency selective filters ofelectromagnetic radiation.

It is yet another object of the invention to provide an improved systemand method for organizing disparate components using holographic opticaltraps to position selectable components in a quasicrystallineheterostructure for establishing chemical, biological and physicalproperties for a desired technological application.

It is also an object of the invention to provide an improved system,method of manufacture and article of manufacture with deliberatelyincorporated defects for programmably achieving a variety of electrical,optical, magnetic, mechanical, biological and chemical properties andapplications.

It is yet an additional object of the invention to provide an improvedmethod and article of manufacture of a quasicrystal with replacedspheres or other components of different size or shape to modify localphotonic characteristics of the quasicrystal.

It is a further object of the invention to provide an improved methodand article of manufacture with selective replacement of one or morespheres on other molecular component geometries of different chemicalcomposition or at different sites than a given quasicrystalline site tocreate new properties or break the quasicrystalline symmetry to createnew properties for a variety of applications.

It is another object of the invention to provide an improved method andarticle of manufacture of a quasicrystal with a particular domain havinga topological defect, such as a phase slip, like a grain boundary inordinary crystalline molecules, thereby giving rise to new usefulproperties.

It is another object of the invention to provide an improved method andarticle of manufacture of two or more quasicrystalline domains createdby holographic trap manipulation to create higher order structures withthe resulting combination having optical properties selected from eachcomponent domain.

It is still an additional object of the invention to provide an improvedmethod and article of manufacture for creating combinations of one ormore quasicrystalline domains with one or more crystalline domains tocreate useful higher order structures.

It is a further object of the invention to provide an improved methodand article of manufacture involving assembly of crystalline andquasicrystalline domains using optical tweezers and/or other particleforce assembly methodologies including self assembly, electropheresis,and optical gradient fields to create useful combination structures.

These and other objects, advantages and features of the invention,together with the organization and manner of operations thereof, willbecome apparent from the following detailed description when taken inconjunction with the accompanying drawings described below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) illustrates a view of silica spheres organized by holographicoptical tweezers into a planar pentagonal quasicrystal (the scale barindicates 5 micrometers); FIG. 1( b) illustrates a heptagonalquasicrystalline domain; FIG. 1( c) illustrates an octagonalquasicrystalline domain arrangement; and FIG. 1( d) illustrates anoctagonal quasicrystalline domain with an embedded waveguide

FIG. 2( a) illustrates a first of four views of an icosahedron assembledfrom dielectric colloidal spheres using holographic optical traps; FIG.2( b) illustrates a second view with a 2-fold symmetry axis; FIG. 2( c)illustrates a third view with a 5-fold symmetry axis and FIG. 2( d)illustrates a fourth view midplane; FIG. 2( e) illustrates theprogressive assembly of the colloidal quasicrystal illustrated in FIG.2( a)-(d); and

FIG. 3( a) shows a holographic assembly of a three dimensional colloidalquasicrystal with the particles trapped in a two dimensional projectionof a three dimensional icosahedron quasicrystalline lattice; FIG. 3( b)shows particles displaced into the fully three dimensional configurationwith the shaded region the one embedded icosahedron; FIG. 3( c) showsreducing the lattice constant to create a compact three dimensionalquasicrystal; and FIG. 3( d) illustrates a measured optical diffractionpattern displaying 10-fold symmetric peaks for the constructedquasicrystal; and FIG. 3( e) illustrates the progressive assembly of thecolloidal quasicrystal illustrated in FIG. 3( a)-(d).

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A system and method have been developed for the construction ofquasicrystalline heterostructures for a wide variety of technologicalapplications. Various articles of manufacture and compositions of mattercan be prepared. In a most preferred embodiment, holographic opticaltraps are used as the starting tool to position a selected particle in agiven position. Therefore, in the preferred embodiment the approach isbased on the well known holographic optical trapping technique in whichcomputer-generated holograms are projected through a high numericalaperture microscope objective lens to create large three dimensionalarrays of optical traps. In our implementation, light at 532 nm from afrequency doubled diode-pumped solid state laser (Coherent Verdi) isimprinted with phase only holograms using a liquid crystal spatial lightmodulator (SLM) (Hamamatsu X8267 PPM). The modified laser beam isrelayed to the input pupil of a 100× NA 1.4 SPlan Apo oil immersionobjective mounted in an inverted optical microscope (Nikon TE2000U),which focuses it into optical traps. The same objective lens is used toform images of trapped objects by using the microscope's conventionalimaging train. As a soft fabrication technique, holographic assemblyrequires substantially less processing than conventional methods such aselectron beam lithography and can be applied to a wider range ofmaterials. Assembly with holographic optical traps lends itself readilyto creating nonuniform architectures (e.g., microstructuralarrangements, articles of manufacture and compositions of matter) withspecifically engineered features, such as the channel embedded in theoctagonal domain in FIG. 1( d). Such structures can, for example, act asnarrowband waveguides and frequency-selective filters for visible light.

Holographic trapping's ability to assemble free-form heterostructuresextends also to three dimensions. The sequence of images of a rollingicosahedron in FIG. 2( a)-(d) show how the colloidal spheres' appearancechanges with distance from the focal plane. This sequence demonstratesthat holographic trapping with a single laser beam can successfullyorganize spheres into vertical stacks along the optical axis, whilemaintaining one sphere in each trap.

The icosahedron itself is the fundamental building block of a class ofthree dimensional quasicrystals, such as the example in FIGS. 3( a)-(d).Building upon our earlier work on holographic assembly, we assemble athree dimensional quasicrystalline domain by first creating a twodimensional arrangement of spheres corresponding to the planarprojection of the planned quasicrystalline domain (see FIG. 3( a)).Next, we translate the spheres along the optical axis to their finalthree dimensional coordinates in the quasicrystalline domain, as shownin FIG. 3( b). One icosahedral unit is highlighted in FIGS. 3( a) and(b) to clarify this process. Finally, the separation between the trapsis decreased in FIG. 3( c) to create an optically dense structure. Thisparticular domain consists of 173 spheres in 7 layers, with typicalinterparticle separations of 3 μm.

The completed quasicrystal was gelled and its optical diffractionpattern recorded at a wavelength of 632 nm by illuminating the samplewith a collimated beam from a HeNe laser, collecting the diffractedlight with the microscope's objective lens and projecting it onto acharge-coupled device (CCD) camera with a Bertrand lens. The welldefined diffraction spots clearly reflect the quasicrystal's five-foldrotational symmetry in the projected plane.

Holographic assembly of colloidal silica quasicrystals in water iseasily generalized to other materials having selectable optical,electrical, magnetic, chemical and mechanical properties for a widevariety of technological applications. Deterministic organization ofdisparate components under holographic control can be used to embed gainmedia in photonic band gap (PBG) cavities, to install materials withnonlinear optical properties within waveguides to form switches, and tocreate domains with distinct chemical functionalization. Thecomparatively small domains we have created can be combined into largerheterostructures through sequential assembly and spatially localizedphotopolymerization. In all cases, this soft fabrication process resultsin mechanically and environmentally stable materials that can beintegrated readily into larger systems.

Beyond the immediate application of holographic trapping to fabricatingquasicrystalline materials, the ability to create and continuouslyoptimize such a variety of articles of manufacture and compositions ofmatter enables new opportunities for achieving heretofore unattainableproducts and perform processes not possible. Many other functionalitiescan be performed, such as evaluating the dynamics and statisticalmechanics of colloidal quasicrystals. The optically generatedquasiperiodic potential energy landscapes described herein also canprovide a flexible model system for experimental studies of transportthrough aperiodically modulated environments.

In other embodiments, the above described methods of fabricating andmanipulating quasicrystalline structures can further be employed tomanipulate compositions of matter to introduce a variety of particulardefects which can establish useful electrical, optical, biological,mechanical, magnetic and chemical attributes. Due to the many degrees offreedom available by virtue of the ability to establish thesequasicrystalline structures and associated defects, one can achievenumerous different physical, mechanical and chemical properties, many ofwhich are unachievable with crystalline or amorphous structures. Theseproperties can be used in a wide variety of commercial areas spanningthe electronics, computer, biological, chemical, optical, mechanicalproperties and magnetics fields.

The technique further permits the manufacture of quasicrystals withreplacement of spheres, or other components, with different size orshape spheres or different size or shape components, enablingmodification of properties, such as, for example, photoniccharacteristics. This concept can also be applied to replace spheres orother size and shape component groups at selected locations withconstituents of different chemical, mechanical, electrical, magnetic oroptical character, thereby allowing controlled designs ofquasicrystalline arrangements with different selectable propertiesuseful in many commercial fields.

In other embodiments domains of quasicrystals can be selectivelymodified to introduce phase slip boundaries, similar to grain boundariesin crystalline materials, to develop properties of interest forcommercial exploitation. In addition, two or more quasicrystallinedomains can be created by optical trap manipulation of particles togenerate higher order structural components with physical and/orchemical properties characteristic of the properties of each componentdomain. In addition, such combinations can be integrated withcrystalline domains to create further higher order structures forselectable commercial applications.

The assembly of all these structures can be accomplished not only by useof optical tweezers but also by other particle force movement forcesources. These other force movement sources can be used alone or incombination with the optical tweezers and these other particle forcesources can include at least one of self assembly, other photonicmethodologies and controllable electrical and magnetic fields. Thesemethodologies allow controlled construction of virtually any desiredstructure exhibiting a wide range of programmed physical, biological orchemical properties.

The following non-limiting example describes one method of assemblingcolloidal particles as a quasicrystal.

EXAMPLE

Colloidal silica microspheres 1.53 μm in diameter (Duke Scientific Lot5238) can be organized by first being dispersed in an aqueous solutionof 180:12:1 (wt/wt) acrylamide, N,N♦methylenebisacrylamide anddiethoxyacetophenone (all Aldrich electrophoresis grade). This solutionrapidly photopolymerizes into a transparent polyacrylamide hydrogelunder ultraviolet illumination, and is stable otherwise. Fluiddispersions were imbibed into 30 μm thick slit pores formed by bondingthe edges of #1 coverslips to the faces of glass microscope slides. Thesealed samples were then mounted on the microscope's stage forprocessing and analysis.

Silica spheres are roughly twice as dense as water and sediment rapidlyinto a monolayer above the coverslip. A dilute layer of spheres isreadily organized by holographic optical tweezers into arbitrary twodimensional configurations, including the quasicrystalline examples inFIGS. 1( a)-(d). FIGS. 1( a), (b) and (c) show planar pentagonal,heptagonal and octagonal quasicrystalline domains, respectively, eachconsisting of more than 100 particles. Highlighted spheres emphasizeeach domain's symmetry. These structures all have been shown to act astwo dimensional PBG materials in microfabricated arrays of posts andholes. FIG. 1( d) shows an octagonal quasicrystalline domain with anembedded waveguide.

While preferred embodiments have been illustrated and described, itshould be understood that changes and modifications can be made thereinin accordance with one of ordinary skill in the art without departingfrom the invention in its broader aspects. Various features of theinvention are defined in the following claims.

What is claimed is:
 1. A method for assembling a heterostructure havingselectable properties, comprising: providing a plurality of particles ofpredetermined character selected from the group of size, shape,biological property or chemical property; providing a particle movementforce to establish a particular quasicrystalline arrangement, theparticle movement force selected from the group of self assembly forces,photonic based methodologies, controlled electrical field forces andcontrolled magnetic field forces; arranging the plurality of particlesinto a three dimensional form of the quasicrystalline arrangement usingthe particle movement force to establish a quasicrystalline arrangementof the particles.
 2. The method as defined in claim 1 further includingat least one of the steps of establishing a defect state in thequasicrystalline arrangement, replacing at least one of the plurality ofparticles with a particle of different size or shape or property,establishing a different quasicrystalline domain within thequasicrystalline arrangement, mixing in a crystalline domain with thequasicrystalline arrangement and arranging the plurality of particles byself assembly.
 3. The method as defined in claim 1 further including thestep of forming the particular quasicrystalline arrangement of theplurality of particles with a preselected symmetry unachievable bycrystalline materials.
 4. The method as defined in claim 1 wherein thestep of providing the plurality of particles comprises using at leastone of microparticles, nanoparticles, large molecules, and biologicalcells.
 5. The method as defined in claim 1 further including the step offorming the quasicrystalline arrangement and establishing a selected oneof a photonic band gap, a chemical functionality, an electricalconductivity attribute, a biological attribute and a magnetic attribute.6. The method as defined in claim 1 wherein the chemical functionalitycomprises catalytic activity, the electrical conductivity attribute isselected from the group of metallic, semiconducting and superconducting;the magnetic attribute comprises a high magnetic flux exhibited by theplurality of particles, a first one of the chemical functionalitycomprises a preselected changed chemical property and a second one ofthe chemical functionality comprises a change in a property over acorresponding crystalline structure composed of same chemicalcomposition.
 7. The method as defined in claim 1 further including thestep of dynamically altering the particular arrangement for achievingdifferent ones of the selectable properties for a selected application.8. The method as defined in claim 1 wherein the selected applicationcomprises at least one of changing a quasicrystalline property selectedfrom the group consisting of mechanical properties, electricalproperties, chemical properties, magnetic properties and biologicalfunctionality.
 9. The method as defined in claim 1 further including thestep of applying at least one of an electromagnetic field, an electricalfield and a magnetic field to further modify properties of thequasicrystalline arrangement.
 10. A method of assembling aheterostructure having selectable properties, comprising: providing aplurality of particles of predetermined character selected from thegroup of size, shape, biological property or chemical property;providing a particle movement force to establish a particularquasicrystalline arrangement; and arranging the plurality of particlesinto a three dimensional arrangement by using the particle movementforce to establish a quasicrystalline three dimensional arrangement ofthe particles.
 11. The method as defined in claim 10 further includingat least one of the steps of establishing a defect state in thequasicrystalline arrangement, replacing at least one of the plurality ofparticles with a particle of different size or shape or property,establishing a different quasicrystalline domain within thequasicrystalline arrangement, mixing in a crystalline domain with thequasicrystalline arrangement and arranging the plurality of particles byself assembly.
 12. The method as defined in claim 10 further includingthe step of forming the particular quasicrystalline arrangement of theplurality of particles with a preselected symmetry unachievable bycrystalline materials.
 13. The method as defined in claim 10 wherein thestep of providing the plurality of particles comprises using at leastone of microparticles, nanoparticles, large molecules, and biologicalcells.
 14. The method as defined in claim 10 further including the stepof forming the quasicrystalline arrangement and establishing a selectedone of a photonic band gap, a chemical functionality, an electricalconductivity attribute, a biological attribute and a magnetic attribute.15. The method as defined in claim 10 wherein the chemical functionalitycomprises catalytic activity, the electrical conductivity attribute isselected from the group of metallic, semiconducting and superconducting;the magnetic attribute comprises a high magnetic flux exhibited by theplurality of particles, a first one of the chemical functionalitycomprises a preselected changed chemical property and a second one ofthe chemical functionality comprises a change in a property over acorresponding crystalline structure composed of same chemicalcomposition.
 16. The method as defined in claim 10 further including thestep of dynamically altering the particular arrangement for achievingdifferent ones of the selectable properties for a selected application.17. The method as defined in claim 10 wherein the selected applicationcomprises at least one of changing a quasicrystalline property selectedfrom the group consisting of mechanical properties, electricalproperties, chemical properties, magnetic properties and biologicalfunctionality.
 18. The method as defined in claim 10 further includingthe step of applying at least one of an electromagnetic field, anelectrical field and a magnetic field to further modify properties ofthe quasicrystalline arrangement.